Freelensing means you take photos with the lens detached from the camera but held in place and moved around to focus. This also lets extra light in sometimes causing light leaks and giving a vintage look and feel.

With vintage-style photos becoming a popular trend with cellphone cameras, this is a neat trick to get the effect the old fashioned way. So what does it look like? I recorded some video while freelensing to take a peek into my DSLR's sensor during the process:

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Freelensing is a fun way to get some neat focus effects, but because your lenses are meant to be mounted to your camera you run the risk of letting in dust. Fortunately, most cameras have sensor cleaning functions that work pretty well but definitely keep dust in mind when giving freelensing a try.